LAKE STEVENS — Joshua Kelly told investigators he “should’ve known better” after he allegedly shot and killed a man in a Lake Stevens apartment last month, according to new charges filed in Snohomish County Superior Court.

Prosecutors charged Kelly, 22, with both second-degree murder and first-degree manslaughter last week in the slaying of Neil Forestier, 27. After the two “playfully” fought and tested the strength of their punches at a home in the 1700 block of 16th Street NE, Kelly picked up a gun from the kitchen counter and shot Forestier in the chest, according to court documents.

Deputy prosecutor Elise Deschenes said prosecutors have evidence to charge Kelly with both felonies, giving a future jury the option to convict him of either.

“I know how to handle a gun. Like I know the gun safety rules, I’ve played with games with guns,” Kelly reportedly told investigators. “I’ve done airsoft wars. Like I should know better.”

On the night of Dec. 30, Forestier, of Arlington, had gone out to the Creekside Alehouse & Grill in Lake Stevens, with a woman he’d been dating. Kelly, an acquaintance, met them there, according to a police report filed in Everett District Court. When the alehouse closed at 2 a.m. Sunday, the three went back to the woman’s apartment, where they danced, sang karaoke and looked for her cat.

Kelly told investigators he recalled Forestier using a gun-shaped flashlight during the search, according to the charging papers.

Around 3:30 a.m., the two men began roughhousing, agreeing to use “10%” strength, a police report read. Before the fight, Kelly reportedly watched Forestier set his holster and handgun on the kitchen counter. The two punched each other in the stomach. Forestier’s blows were much more powerful than Kelly’s, the defendant told investigators. Forestier, who had moved to Washington from Illinois, was an amateur mixed martial arts fighter, with his last fight recorded in 2018, according to the database Tapology.

Kelly picked up the firearm and aimed it at Forestier, charging papers say. Forestier turned away from the defendant, and pulled the trigger, prosecutors allege.

Forestier died at the scene from a gunshot wound to the torso, the Snohomish County Medical Examiner’s Office determined.

Kelly initially told investigators he thought the gun was a flashlight and intended to shine a light on Forestier, charges say. He reportedly later acknowledged this story was not believable.

When detectives challenged him in a second interview, he admitted knowing it was a firearm when he picked it up, according to the charges.

The defendant told investigators he did not know if it was a real gun or a BB gun, or if it was loaded. He intended to scare Forestier “a little bit, but not a lot,” the charges say.

This week, Kelly remained in the Snohomish County Jail with bail set at $250,000. Court records show he has no criminal history.

Maya Tizon: 425-339-3434; maya.tizon@heraldnet.com Twitter: @mayatizon.