That person said someone was talking about carrying out a campus shooting. Mitchell said the person asked the sender if he was kidding, and the response "led the person to believe it was a serious threat." At 4 a.m., Mitchell said, a third person called police, also after seeing a posting about a campus shooting on the omegle site.
By 4:45 a.m., Mitchell said, police had isolated the computer from which the messages were sent to the College Park campus, and by 6 a.m. they had identified Song. Officers set up surveillance and went inside his dorm room at 7:30 a.m., but he wasn't there. Mitchell said police arrested Song as he returned to the dorm in a vehicle at 10:06 a.m.
Police said they searched Song's car and dorm room, along with his parents' house in Fulton, but would not describe what, if anything, they seized. Mitchell said no weapons were found at any of the three locations.
Song does not have an adult criminal record, according to the Maryland courts, but did receive a traffic ticket on the College Park campus for failure to stop at a stop sign while coming out of a campus parking lot last year. He paid a $90 fine.
When Song was 12, court records show, he was hit by a car while he was skateboarding out of his driveway and onto Brookwood Farm Road. His father sued the vehicle owner's insurance company, GEICO, and won a $39,400 settlement to pay his son's hospital bills at Children's National Medical Center, according to court documents.
The house in which Song grew up in Fulton, in a small development near Route 216 and U.S. 29, was quiet on Monday. His parents live in the 8100 block of Brookwood Farm Road, which ends in a cul-de-sac lined with large single-family homes on land that once was part of farms.
State tax records show that Alexander Y. and Jenna Song bought the red-brick 3,600-square-foot home in 1999 for $475,000. It is now assessed at $738,500, with 1.3 acres. No one was home Monday morning.
The house is about two miles from the 1,500-student Reservoir High School, where Song attended four years of high school.
Howard County schools spokeswoman Patti Caplan said that Song was "a very good student academically" and had been a member of the National Honor Society, the National Art Honor Society, the National Spanish Honor Society, and the film and German clubs.
At College Park, Song was accepted into Gemstone, an honors group made up of mostly science students. It is a particularly intense program in which students spend four years researching a single project and are assigned to groups working with a single professor throughout their studies.
Song was part of a group called "Be Pure," and according to Gemstone's director, James Wallace, he and his classmates were working on a project to convert methane gas into an energy source. Members of his study group could not be reached Monday, and Wallace declined to talk about Song.
Professor Steven Hutcheson, Song's Gemstone adviser, told the Associated Press that Song had been one of the team's more vocal members and had been excited by the project. He also said Song had recently appeared quieter but said there was no indication he was unhappy or capable of violence.
"I wish there had been something, because I would have loved to have helped him," Hutcheson said.
The campus newspaper, The Diamondback, identified Song's roommate as Brian Barnett, and said he was awakened Sunday morning by police.
"They were looking for my roommate; they didn't tell me any information, just asked questions about what I knew, and I didn't know anything," the sophomore biology and psychology major told the newspaper. "I know he's been stressed recently, but that's all I know. I assumed it was schoolwork."
An earlier version of this story gave the incorrect first name of Alexander G. Song 2nd's mother. The Baltimore Sun regrets the error.
Timeline of arrest
Saturday, 9:23 p.m.: An alumnus calls campus police after seeing an anonymous posting on a website from a person claiming to be threatening a "shooting rampage."
Sunday, 1:30 a.m.: An anonymous caller from Montana calls police after receiving a message in an Internet chat room about a campus shooting. He asked if the person was kidding, and got a response that "led the person to believe it was a serious threat."
Sunday, 4 a.m.: Police get another tip from an Internet user about a threat on campus.
Sunday, 4:45 a.m.: Authorities isolate the computer used to send the threatening messages as being on the College Park campus
Sunday, 6 a.m.: Police identify Alexander G. Song as the alleged sender and establish surveillance on his dorm at Oakland Hall.
Sunday, 7:30 a m.: Police go into Song's dorm, but he isn't there. Roommate tells them he stepped out but was returning shortly.
Sunday, 10:06 a.m.: Police arrest Song as he parks near his campus dorm.
Source: University of Maryland, College Park Police Text NEWS to 70701 to get Baltimore Sun local news text alerts