The homicide trial of a Muddy Creek Township man who claims he accidentally shot his friend to death in 2014 kicked off Monday, with state police investigators testifying they quickly saw through statements given by the defendant and noted his “calm” and “self-centered” behavior during their investigation.

Jeremey D. Sickenberger, 25, faces one count of criminal homicide after an incident on April 17, 2014, which resulted in the death of Thomas “T.J.” Stockman, 21, of Portersville.

Police have said that Sickenberger, Stockman and several other people had gathered that evening at Sickenberger’s mobile home on Robbie Way when Sickenberger shot Stockman in the side of his chest with a .22-caliber rifle.

From the beginning Sickenberger has claimed the shooting — the bullet pierced Stockman’s heart, severed his aorta and hit his lung, killing him “almost instantly,” said Butler County District Attorney Richard Goldinger — was an accident.

Whether that accident constitutes murder or criminally negligent homicide depends on which attorney you ask. Goldinger, in his opening statement Monday, told jurors that prosecutors would prove Sickenberger’s conduct merited a third-degree-murder conviction with testimony on how he attempted to hide the truth from police and that he did, in fact, know the gun that killed Stockman was loaded.

Sickenberger, in statements to police, has said he believed the gun was a pellet gun and that it was unloaded when he pointed it at Stockman that night. He has also told police that he doesn’t remember if he pulled the weapon’s trigger. But Goldinger, in his opening, said there was no doubt that Sickenberger had done just that.

“Pointing a loaded firearm into somebody’s chest and pulling the trigger is at least malice,” Goldinger said. “It is certainly disregard for human life.”

Defense attorney Joe Smith disagreed, calling Stockman’s death a “tragedy” that Sickenberger relives “every time he opens his eyes,” and a textbook case of involuntary manslaughter, which only requires “reckless and grossly negligent,” conduct, not malice.

“It’s like that glass slipper fitting onto Cinderella’s foot,” Smith said. “That’s what this case is.”

Trooper Michael Taylor, the lead investigator on the case, said it was quickly apparent that Sickenberger’s story — he initially claimed the gun accidentally discharged after being kicked — didn’t add up. But as state police investigators pressed Sickenberger for the truth, Taylor said, the defendant acted in a way he didn’t expect.

“He didn’t get emotional during the interviews, and I found that odd,” Taylor testified. “In my opinion, he was concerned more about himself than the victim.”

Taylor and Trooper Chris Birckbichler, a criminal investigator with PSP, both interviewed Sickenberger multiple times during state police’s investigation into Stockman’s death, they both testified. Both testified that Sickenberger’s version of events changed multiple times, and both said they noted how calm, collected and self-involved he appeared to be.

Pressed by defense attorney Joseph Smith on Sickenberger’s state of mind, Birckbichler acknowledged that he had told troopers that he was “terrified” and that things were a “blur” to him. But the trooper said he took the statement to be “self-centered,” and maintained that Sickenberger was “very calm,” throughout all his interactions with state police.

“I believe he was scared for the outcome of this investigation,” Birckbichler said.

Prosecutors entered a number of photographs into evidence on Monday, including photographs of a bloody shirt investigators say Stockman was wearing the night he was shot.

As testimony regarding the photographs progressed, Sickenberger, who appeared in court Monday dressed in a suit and tie, hung his head and wiped at his eyes multiple times.

Prosecutors also played taped phone conversations Sickenberger had with a Butler County 911 dispatcher and state police in the immediate aftermath of the shooting that evening.

On the tapes Sickenberger sounds calm and composed as he tells the 911 dispatcher he believes Stockman is critically wounded.

“It’s (the bullet wound) right near his heart, you guys need to get here,” Sickenberger says to the dispatcher on the recording.

When the dispatcher asks if Stockman is conscious, Sickenberger says “he’s there, kinda.”

The 911 dispatcher then transfers Sickenberger to state police, where he briefly exchanges pleasantries with a woman on the line before telling her that Stockman has lost consciousness.

“I don’t think so. Not really,” he says when asked if Stockman is conscious.

Butler County District Attorney Richard Goldinger said that he anticipates resting the prosecution’s case against Sickenberger today, after prosecutors call to the stand a state police firearms expert, a medical official from the Allegheny County Medical Examiners Office, and Paul Pfaff, the owner of the gun that killed Stockman.

Defense attorney Joseph Smith, who is representing Sickenberger, declined Monday to comment on the trial.