A Calhoun College junior was arrested Monday and suspended from the University after allegedly firing a handgun inside the Beta Theta Pi fraternity house — leading police to discover a cache of weapons, including an AK-47, in his bedroom.

David Light ’09, 21, was charged with several weapons-related crimes, and police seized two illegal assault rifles and nine other firearms from his room at the fraternity house at 36 Lynwood Place, police said. Potentially dangerous chemicals were also discovered in Light’s room, according to witnesses and police, and the Yale Police Department said more charges could be filed against Light as the investigation continues.

Light, a resident of Woodland Park, Colorado, was charged with two counts of illegal possession of assault rifles, unlawful discharge of a firearm, reckless endangerment in the first degree, threatening in the second degree and breach of peace in the second degree.

A visitor to the fraternity was in a second-floor bedroom at around 3 a.m. Friday when he heard gunshots, according to a police affidavit. The visitor, Christopher Keefer, went downstairs to the house’s common room and found Light with a gun in his hand and several shell casings on a nearby coffee table, according to the warrant.

Keefer, a member of an unnamed branch of the armed forces who was visiting his brother at the fraternity house, recognized the weapon as a semiautomatic pistol and asked Light to put the gun down. Light, who had been drinking heavily, responded that he was only firing blanks and proceeded to fire two rounds into the ceiling of the room, according to the affidavit. Pressed on whether or not what he was doing was safe, Light is said to have responded, “Why don’t I point it at your head to find out?”

Keefer notified a YPD sergeant on Sunday of what he had observed, and said Light had showed him his stockpile of weapons several days before the Friday morning incident.

Police also interviewed a maintenance worker who had changed the door locks of Keefer’s room on Sunday, according to the affidavit. The worker said he spotted a pistol in a belt holster sitting on a table as well as a new, .50 caliber sniper rifle on the floor of the bedroom, in addition to about a dozen boxes of ammunition.

After obtaining a warrant, YPD officers searched the fraternity on Monday night and arrested Light.

Two students who were at Beta during the seach on Monday night said about six law enforcement officials, one in body armor, entered the fraternity at around 10:30 p.m. to conduct a search and arrest Light. Police ordered everyone to stay put, said Rachel Oppenheimer, a rising sophomore at Kenyon College who is staying in New Haven this summer.

Forty-five minutes later, police said they had found bomb-making materials and evacuated the house, Oppenheimer said. The New Haven Fire Department was called to the fraternity and remained there for several hours early Tuesday morning after police found hazardous materials during their search, Assistant Fire Chief Ralph Black said Wednesday.

Another student, who had stayed at the house for a few days before moving into University housing, said he once saw Light carrying two large firearms up the stairs inside the house, and another time saw a “serious-looking” high-powered rifle at the fraternity, which he thought was suspicious.

“Last night, it fell into place,” he said. “I felt foolish that I didn’t tell someone.”

Around Yale, Light was widely known as a gun enthusiast, and his large gun collection was not something he tried to keep hidden, students said. On his Facebook profile, which was removed Tuesday afternoon, Light listed pyrotechnics, weaponry and firearms among his interests.

“It wasn’t very much of a secret at all,” said David Koppstein ’08, who took an advanced biology course with Light. “He talked about it. I wasn’t sure about the details, which guns he had specifically, but he just seemed to enjoy that in general.”

A local television report showed photographs of Light, reportedly from his MySpace page, posing with guns. Light described himself on his Facebook profile as a member of the New Haven Sportsman’s Club, a gun range in Guilford, and a member of the club confirmed that Light was a regular there. The student who lived in Beta said he saw Light with a target, the type that would be used at a rifle range.

The club member, who declined to give his name, said Light was a bright student whose interest in guns was not a threat to anyone.

“He’s a perfectly normal person,” he said. “He’s not a crazy guy. To be honest … things always get blown out of proportion when it comes to arrests with firearms.”

Light is a member of Beta and is president of Chabad at Yale, a Jewish student group. A biology major, Light listed himself on Facebook as a member of the Yale Class of 2008, though the University identifies him as a rising junior.

Classmates described Light as a top-notch student, and some suggested his interest in the sciences might explain the chemicals that were found in his residence.

According to his Facebook page, Light works for Guilford-based RainDance Technologies, a nanotechnology start-up, researching market opportunities and recruiting investors. In 2005, Light worked in the Center for High Technology Materials at the University of New Mexico, focusing on microchip research.

Officials at RainDance could not be reached late Tuesday, nor could the New Mexico professor who supervised Light’s research.

The weapons seized from Light’s residence included an AK-47 assault rifle, an AR-15 assault rifle, a .50-caliber sniper rifle, a Russian M-91 infantry rifle, a 12-gauge shotgun, several pistols and four to five thousand rounds of mixed ammunition, New Haven Police Department assistant chief Stephanie Redding said.

The AR-15 and AK-47, considered assault rifles by state statue, are illegal to own by Connecticut law. Possession of an assault weapon is a Class D felony with a mandatory minimum sentence of one year in prison, unless it is a first-time offense and the weapon was legally acquired before the state’s assault weapons ban went into effect in 1993.

Light does have long guns — which could include firearms like rifles and shotguns — registered to him, but did not have a pistol permit, according to the police affidavit.

Light was known not just as a gun enthusiast but as a collector as well, according to students. The M-91 infantry rifle, for instance, was last produced during World War I and is considered a collectible, likely worth hundreds of dollars.

A student who lived a floor above Light during their freshman year said he had heard about Light’s gun collection from his suitemates.

“They weren’t weapons he was using, as far as I know, like people who have an interest in swords of that kind of thing,” the student said. “I really do think it was a collector kind of thing.”

Weapons are expressly forbidden in Yale dormitories, though the Executive Committee, the University’s disciplinary body, rarely comes across cases involving that rule being broken.

In 2005, the most recent year for which statistics are available, one sophomore was reprimanded by ExComm for a weapons-related offense. In the seven years prior to that, the only students brought before ExComm on weapons charges were a few students caught with BB guns, according to the committee’s annual reports.

After his arrest, Light was transferred into the custody of the New Haven Police Department, the University said.

Light was released early Tuesday afternoon after posting $150,000 bond, officials said late Tuesday. He is due back in court August 2.

Yale President Richard Levin ordered Light’s suspension, University spokeswoman Helaine S. Klasky said in a statement. Under the Undergraduate Regulations, Levin has the power to order an emergency suspension in order to protect the health or well-being of a member of the University.

“Yale’s action does not convey any judgments about Mr. Light’s guilt or innocence relating to the criminal charges lodged by the State,” Klasky said.

The suspension will remain in effect until the matter is handled by the Executive Committee, the top disciplinary body for undergraduates, which does not meet during the summer, she said.

The YPD’s investigation into Light is continuing and more charges may be filed, YPD chief James Perrotti said, according to the University’s statement. The Connecticut State Police, the NHPD and the FBI assisted the YPD in the investigation, the University said.

–Lea Yu contributed reporting.