A man on trial for the fatal shooting of a St. Louis County police officer had talked on social media and in text messages about wanting to die in a “suicide by cop” encounter and told the fallen officer’s partner to shoot him, prosecutors said Monday in opening statements.

Prosecutors are seeking a first-degree murder conviction, which would send Trenton Forster, 20, to prison for life without parole. They decided not to seek the death penalty for the October 2016 killing of Officer Blake Snyder.

Public defender Stephen Reynolds conceded, meanwhile, that Forster killed Snyder but argued that Forster did not deliberate first, as prosecutors say.

“You’re going to find Trenton Forster guilty of murder, but I’m asking you not to find him guilty of murder in the first degree,” Reynolds said, suggesting second-degree murder as the appropriate charge. That would allow for a life sentence, calculated in Missouri at 30 years, with the possibility of parole.

Snyder, 33, of Edwardsville, Illinois, was killed while responding to a disturbance call in the Green Park area. Police said Forster had a relationship with a girl who lived in a home on the block, and that Forster had been beating on the door.

When Snyder approached Forster, who by then was in a car parked outside the home, Forster opened fire on Snyder, police said. Snyder left behind a wife and 2-year-old son.

Assistant prosecutor Alan Key said that in the week before the shooting, Forster tried multiple times to buy firearms and ammunition at gun stores and pawn shops, but was turned away several times because he appeared to be high. Eventually, someone he smoked marijuana with put him in touch with a private seller, who sold him a pistol and a rifle. A few days later he bought 50 rounds of ammunition at Walmart, Key said.

Snyder approached Forster’s car, saying, “Hey bud, let me see your hands,” Key told the jury. Officer John Becker then saw Snyder fall and unloaded his gun at Forster, hitting him five times.

Key told jurors that Forster said to Becker, “Shoot me, I have a gun,” though Forster’s pistol had jammed.

The trial is expected to run through at least Friday.

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