Tamerlan Tsarnaev could be a bully, a high-school tough guy intent on proving his mettle as a boxer, and an adolescent sometimes eager to put a scare into his peers, his former girlfriend said on Monday. But she never anticipated his involvement in something like the attacks on the Boston Marathon last week.

'When I was in high school he wasn't like that at all,' said Nadine Ascencao, 25 years old, of Brookline, Mass., who said she dated Mr. Tsarnaev, 26, and who court records say was the woman who accused Mr. Tsarnaev of slapping her in 2009. 'I was shocked like everybody else. He was a little tough guy, but I thought that was it. In high school, everybody acts like that. Like a bully guy, you know? Now it's just shocking for me.'

Ms. Ascencao, who records show also lived for a time at an apartment at the same address as Mr. Tsarnaev on Norfolk Street, avoided questions about a 2009 domesticcomplaint against Mr. Tsarnaev. According to the complaint, Ms. Ascencao told police that Mr. Tsarnaev had slapped her face in an argument over another woman. According to the complaint, Mr. Tsarnaev admitted slapping Ms. Ascencao and was arrested on charges of assault and battery. The charges were dismissed before trial.

'He was always tough,' Ms. Ascencao said, but 'never really did anything major.'

Ms. Ascencao said she had been deluged by phone calls since Mr. Tsarnaev and his brother, Dzhokhar, were identified as suspects in the Boston Marathon bombings. The inquiry is the first her family has heard of her dating Mr. Tsarnaev, she said, adding that the two attended high school together.

Ms. Ascencao said Mr. Tsarnaev sought to project an aura of toughness, but he wasn't a violent person when she knew him. In a brief telephone interview, she didn't say how long they dated or when it ended.

'He was just like a normal person that sometimes like wanted to scare kids in high school but that was it,' she said. 'Just a tough guy.'

Since learning of Mr. Tsarnaev's alleged involvement in the bombings, and subsequent death during a shootout with police Thursday night, Ms. Ascencao said, 'I didn't even cry or anything.'

'I'm just shocked and disgusted that they did that,' she said. 'I can't believe they were capable of doing such a thing.'

Ms. Ascencao's neighbors said her home was visited Friday by Federal Bureau of Investigation agents. One neighbor, a 50-year-old woman who gave her first name as Felina, said she woke at 6:15 a.m. to find about 10 agents wearing FBI vests at a house that Ms. Ascencao shares with three others.

According to Felina, the agents told her, 'They found a number in a phone, and they were there to clarify their relationship.'

The agents left around 9:15 a.m., she said. Felina said about four agents returned around 1:30 p.m. and left 15 minutes later.