In the days before police say he was fatally shot by his roommate Dayvon Green outside their College Park home, University of Maryland senior Stephen Rane had expressed concerns about Green having a mental illness and owning guns, according to a close friend.

"I know that he did feel uncomfortable in the house," said Drew Needham, a senior who lived with Rane for two years before Rane decided to move off campus into the 36th Avenue home with at least four others, including Green, a 23-year-old graduate engineering student. "He'd stayed at some other friends' houses recently."

Still, the relationship between all the roommates had seemed generally "amicable," Needham said, and Rane's concern had not reached a level where he predicted violence.

"He knew something was wrong, but nobody expects something like this," said Needham, a 21-year-old biology major, who described his friend as an open-minded, gregarious student.

According to police, Green also wounded a second roommate before killing himself early Tuesday morning. Since then, more details about Green's demeanor and background have emerged.

One revelation: Green briefly worked for the university Police Department as a student aide last year — a position that does not carry much authority but does require a background check. Campus police found a record of his two-week stint during a review of university records pertaining to Green.

"We said, 'Oh, look at that,'" said Maj. Marc Limansky, a police spokesman.

Limansky said student police aides perform duties such as directing traffic during special events and manning security desks in the student union and other buildings while officers conduct patrols through the buildings.

"They have no enforcement authority, no weapons, no access to weapons, no access to records," Limansky said.

Still, the aides are screened. Before they are hired, officers check gun ownership, wanted lists, driver's license records and criminal records throughout the broader Chesapeake Bay area, Limansky said. Green passed all the checks.

Green owned a 9 mm handgun at the time of his employment and would have been told that he could not bring it on campus or in the workplace, Limansky said. He said student aides are not subject to a mental health assessment, unlike officers within the department.

"There was nothing unusual whatsoever coming back to indicate anything negative," he said of the check.

On Tuesday, Prince George's County Police say Green shot two of his undergraduate roommates with a 9 mm handgun after drawing them outside by lighting small fires in and around their shared home. Green's family told police he had been suffering from a mental illness for at least a year and had been on medication for a time.

Rane, 22, of Silver Spring was killed in the home's front yard, and Neal Oa, 22, of Frederick County was shot in the leg while fleeing. Green then killed himself in the backyard, police said. When police arrived, they found the 9 mm near his body, and a bag containing a .22-caliber semiautomatic Uzi, at least three 20-bullet magazines, a machete and a baseball bat nearby.

Brad Bolino, the property's landlord, called the shootings a "terrible tragedy" that had shocked him. "As a parent, it turns your stomach over," he said.

Bolino declined to comment on whether Oa or the other, unidentified tenants were planning on remaining in the home. He said he had not been allowed into the home by police as of Thursday morning and did not know the extent of damage inside, where police say Green started a fire in the basement.

Services for Rane, a Centennial High School graduate who was studying English and linguistics, will be at 10 a.m. Saturday at the Mauger/Givnish Funeral Home in Malvern, Pa.

This week, police and university officials said they had no indication that Green might become violent.

According to many who knew him, the Morgan State University graduate appeared to be a quiet, academically focused high-achiever. He had participated in a NASA program for gifted students, and years ago had served as a mentor to younger students and as a resident assistant at Morgan.