By Mark Ackerman

DENVER (CBS4)- A Denver jury will now decide if the killing of a security guard for Regional Transportation District was premeditated murder.

Joshua Cummings (credit: Denver Police)

During closing arguments, prosecutor Beth McCann said no reasonable person could conclude that Joshua Cummings didn’t plan “this shocking and brutal crime.” She asked the jury to convict him of first degree murder.

Showing the jury surveillance video of the crime, McCann said it was clear Cummings was “stalking” Scott Von Lanken before coming up from behind and shooting him behind the ear.

Scott Von Lanken (credit: CBS)

Defense attorneys admitted Cummings shot Von Lanken in front of Union Station on Jan. 31, 2017, but attorney David Rosen argued there was no evidence Cummings planned the shooting.

(credit: CBS)

“The sole question for you is what was Cumming’s mental state? What did he intend?” Rosen told the jury as he proposed an alternative theory that the Cummings struggled with Von Lanken and there was an accidental discharge of the gun.

Wearing a suit, tie and an eight-inch beard, Cummings was engaged with his defense team the entire trial.

The 8 man and 3 woman jury will resume deliberations Thursday morning.

Mark Ackerman is a Special Projects Producer at CBS4. Follow him on Twitter @ackermanmark