MSU mass shooting: Suspect's handguns were legally purchased

Classes at Michigan State University, which were canceled this week in the wake of Monday night's deadly mass shooting, will resume on Feb. 20, school officials said Tuesday.

Meanwhile, an on-campus vigil in honor of the victims, all of whom were students, is scheduled for Wednesday night.

"We are devastated by this tragedy and wrap our collective arms around the victims' families and friends who face unimaginable injury and loss," MSU's vice president of university advancement, Kim Tobin, said in a statement announcing the details.

Arielle Anderson, a junior from Grosse Pointe, Michigan, was one of the three Michigan State students killed in the shooting. Her family remembered her as a "precious daughter, granddaughter, sister, niece, cousin, and friend" in a statement shared Tuesday evening through her mother's employer, Comerica Bank.

"As much as we loved her, she loved us and others even more," the family said. "She was passionate about helping her friends and family, assisting children and serving people."

Anderson, who was described as "sweet and loving with an infectious smile," wanted to be a surgeon, her family said.

"Driven by her aspiration to tend to the health and welfare of others as a surgeon, she was working diligently to graduate from Michigan State University early to achieve her goals as quickly as possible," the family said.

"We are absolutely devastated by this heinous act of violence upon her and many other innocent victims," the statement added.

The three Michigan State students killed in the shooting have been identified by university police.

Brian Fraser, a sophomore, and Arielle Anderson, a junior, were both from Grosse Pointe, Michigan.

Alexandria Verner, a junior, was from Clawson, Michigan.

Five other students remain in the hospital in critical condition following the attack.

The FBI offered new details on the suspected gunman in a confidential briefing to law enforcement on Tuesday.

Investigators have determined 43-year-old Anthony McRae walked from his home to Michigan State and had no connection to the university or the victims.

Authorities said that when McRae was found dead from a self-inflicted gunshot wound, he had a “3-page document expressing his reasons for the attack and a number of additional locations in Lansing and Holt, Mich.; Ewing Township and Franklin Park, NJ; and Colorado Springs, Colo., which had ‘hurted’ (sic) him and, therefore, were deserving of attack.” Agents believe he had “personal grievances” with people at those locations.

McRae lived with his father, who is cooperating with the investigation, the FBI reported.

Investigators said the suspect’s writings confirmed he “was often alone.” The briefing said the gunman viewed himself as “a loner” and an “outcast” who was “never noticed or accepted by others.”

-ABC News’ Josh Margolin