Police are investigating the murder of 21-year-old Hofstra University junior, Andrea Rebello, who was shot and killed in an off-campus house during an early morning break-in, Friday. She was studying public relations.

A masked gunman was also killed during the police-involved shooting in the Long Island home she shared with her twin sister, Jessica Rebello, along with a man and another woman. Apart from Andrea, everybody else escaped unhurt.

Nassau County deputy inspector Kenneth Lack said that a man with a ski mask and a gun forced his way into the home at 2:20 a.m., Friday. The armed suspect allowed one of the women to leave the Uniondale home, probably to get cash, but she immediately called 911.

Police arrived at  2:29 a.m. during which the shooting occurred.

"Shortly after our arrival, a shooting took place where the suspect is killed and one of the female victims is killed," Lack said.

Chief of Detectives Rick Capece said that a gun was found inside the home, but no details were provided about who fired the fatal shots and how many shots were fired. Forensics will be used to obtain the specifics.

It's also unclear whether Andrea, native of Tarrytown, N.Y., was killed by the gunman or the police.

Andrea's father  said, "My baby, she was so beautiful. I'm so confused I don't know what to do."

"She was a smart, beautiful girl," recalled Carol Conklin-Spillane, principal at Sleepy Hollow High School, from where the twins graduated in 2010.

A private memorial was held on campus Friday evening for students and faculty.

Hofstra University President Stuart Rabinowitz later issued a statement saying that the whole campus community was shocked by the death of the student

"What we do know is that a young member of the Hofstra family has been taken from us in a senseless act of violence. Our hearts and minds and our thoughts and prayers are with her family, her friends and her classmates."

The officials said that the university's commencement ceremony over the week-end will continue as scheduled.