EVERETT, Wash. » A 19-year-old man accused of shooting three former high school classmates to death at a house party in suburban Seattle last month sent his friends text messages alluding to his plans, including one in which he wrote, “I’m killing everyone at a huge party,” court documents said.

Allen C. Ivanov referred to himself as a “future shooter” in the messages, The Daily Herald newspaper in Everett reported today. He has been charged with three counts of aggravated murder.

He tried to get back together with his former girlfriend the day before the July 30 attack, but she refused, Snohomish County deputy prosecutor Adam Cornell wrote in new charging papers filed today.

Ivanov texted one friend 12 hours before the attack, saying he was going to take a gun safety class before the shooting because he didn’t want to “mess up,” according to the court documents.

The friend told him to go deer hunting instead and stop dwelling on his ex-girlfriend. Investigators said that Ivanov responded: “No. I’m killing everyone at a huge party.”

Later that night, Ivanov sent another text to the friend that read, “I’m 2 minutes from shooting,” the documents said.

About 90 minutes after that, Ivanov began firing his newly purchased assault-style rifle, police said. He was so unfamiliar with the weapon that he read the instruction manual outside the party just before the attack, authorities said.

Jake Long, Jordan Ebner and Ivanov’s ex-girlfriend, Anna Bui, all 19, were killed.

“For two hours prior to the shootings, he surveilled guests at the house party, read an instruction manual for his weapon, and texted a friend about the impending killings,” Cornell, the prosecutor, wrote in court papers about Ivanov. “Soon after he spotted Ms. Bui and a male partygoer interacting, he decided to approach the home with his weapon.”

Will Kramer, 18, also was shot in the back but ran to safety in a nearby wooded area. He called 911 and police took him on the hood of a patrol car to waiting medics, who stayed away from the scene because officers didn’t know if the shooter was still there. Kramer was released from the hospital earlier this week.

Tim Leary, a lawyer for Ivanov, did not immediately return a call from The Associated Press seeking comment today. He previously noted his client’s age and relative immaturity. Leary also has questioned why Ivanov was allowed to buy a rifle when he would have been turned away if he tried to buy a six-pack of beer.

Ivanov was expected to be arraigned Monday. He is being held without bail.