Members of the media pass the crime scene on 36th Avenue in College Park where two University of Maryland students died in a murder-suicide and a third was shot early Tuesday. (Bonnie Jo Mount/THE WASHINGTON POST)

Dayvon Green spread the charcoal in little piles in and around the house he shared with other University of Maryland students. He lit the coals, and smoke crept through the home.

The flames awakened his roommate Stephen Rane about 1 a.m. Tuesday. Rane roused a third student living at the house in College Park, and the two ran outside. With Green, they came up with a plan to put out the fires.

But then Green pulled a 9mm pistol from his waistband. One roommate ran, and Green started firing. When he was done shooting, Green walked around to the back yard and killed himself.

Rane lay dead out front, and the student who ran was seriously wounded.

Police later searched Green’s shoulder pack and found a semiautomatic Uzi rifle with ammunition, a machete and a baseball bat.

The burst of student violence just off campus on 36th Avenue thrust the university to the center of the national debate on mental health and gun control. Green’s family members told Prince George’s County police detectives that he was taking medication for a diagnosed mental illness. Investigators said Green was able to buy both the handgun and the Uzi legally.

In Annapolis, where lawmakers are weighing a package of strict gun-control measures in the aftermath of the mass shooting in Newtown, Conn., several said Tuesday’s deaths added urgency to their efforts.

Police said they do not know whether Green, 23, a graduate engineering student, had any plans beyond the shooting at his home. He did not leave a suicide note or a manifesto threatening additional violence.

Prince George’s police spokeswoman Julie Parker said it would be a “challenge” to determine whether Green had broader intentions.

University officials said Green never sought mental health treatment on campus.

“This is one of those most horrific things,” University of Maryland President Wallace D. Loh said at the shooting scene. “As a parent, I would dread the call that my son, who is at the university he wanted to go to, is dead.”

Stephen Alex Rane, 22, was a senior English major from Silver Spring. No one answered the door at his family’s home Tuesday. Police declined to identify the wounded housemate, a 22-year-old undergraduate student, who was expected to survive.

Chip Cobb, 24, a graduate student who lives next to the house, said he turned off his lights, ducked into a corner and “curled up in a ball” when he heard the shooting. When he emerged after the gunfire, he said, he saw fires in his yard and, soon after, police swarming the neighborhood with guns drawn.

“For me, I’m just grateful that I’m alive and that my friends are alive,” he said.

On Tuesday afternoon, homicide detectives were trying to determine a motive for the shootings or why Green snapped. Authorities said Green, whose family is from the Baltimore area, was a full-time graduate student in engineering who had done his undergraduate work at Morgan State University. He once participated in the NASA Student Ambassadors program.

Clinton R. Coleman, a spokesman for Morgan State, said Green graduated in 2012 with a degree in engineering. Coleman said officials from the University System of Maryland were on campus reviewing the student’s background. He said they picked up documents but did not know what they took.

At least locally, Green’s record bears only a minuscule blemish: an alcohol-related ticket that was dismissed this month. Parker said police had been called to the home twice before: once in October for a burglary in which nothing was taken and again last month when a prank caller referenced “hair on a couch” before hanging up.

University of Maryland Police Chief David Mitchell said his department, too, had received no reports that Green might be a threat.

“He was not on the radar screen at all,” Mitchell said. “It’s just a god-awful tragedy.”

Parker said Green’s family told detectives that Green had battled some type of mental illness for the past year and was taking medication. She declined to be more specific. Law enforcement officials, speaking on the condition of anonymity to candidly discuss the investigation, said he suffered from schizophrenia.

Messages left for Green’s relatives were not returned. After a reporter knocked on the door of the family’s home in the Baltimore suburb of Rosedale, a neighbor emerged and quickly shut the door behind her, saying “no comment” as she walked away.

Two others on the street also declined to talk. But one older man who lives next door to the Greens said: “As far as I know he was a nice young man. He went to college and he was helpful when I needed it.”

How Green obtained the weapons is a part of the police investigation. Law enforcement officials said Green purchased the handgun legally in April from Just Guns, outside of Baltimore. Jim Morganthall, a manager there, said while he could not confirm that specifically, Green would have undergone a background check — as do all gun purchasers — in which his name was checked against certain state mental health records. The check would not explore records at private hospitals, according to a state police spokesman.

The fully loaded semiautomatic weapon in Green’s shoulder pack was a .22-caliber rifle manufactured by Israel Weapons Industries. The model is an Uzi B. Green bought the weapon legally Jan. 18 from a gun store in Silver Spring.

Gov. Martin O’Malley (D) has proposed a ban on assault weapons, strict new licensing requirements and an expansion of the list of mental health issues that can preclude a state resident from purchasing a gun. Green’s Uzi probably would be banned under O’Malley’s bill. Still, it was not immediately clear whether the bill would have prevented Green from purchasing the handgun used in the shooting. O’Malley spokeswoman Raquel Guillory said it was too soon to comment or draw conclusions about the incident.

The shooting comes at a time when police have added patrols on campus in response to at least five armed robberies or attempted robberies at or near the university in recent weeks. One of those cases was later determined to be unfounded, and Mitchell, the U-Md. police chief, said none seem to bear any connection to the shooting.

Even as debate raged from College Park to Annapolis, some officials urged grief for the victims rather than political back and forth.

“For today,” said Loh, the U-Md. president, “I would like to focus on our mourning and our thoughts for the victims.”

Lynh Bui, Aaron Davis, Maggie Fazeli Fard, Peter Hermann, Jennifer Jenkins and Alice Crites contributed to this report.