He has been waiting nearly four years for answers in the shooting of his older sister Belinda Beisly.
She was found dead in her home north of Deerfield in July of 2009
"It's been on my mind every day. There wasn't a day that I wasn't thinking about it or wondering if someone was working on it," he says.
Friday, Irwin finally got that call.
Just after one this afternoon, Vernon County Sheriff's deputies arrested 57-year-old Bob Beisly II at his Nevada home.
He is currently being held at the Vernon County Jail charged with the first-degree murder of his estranged wife.
"He's been a person of interest since the beginning," Investigator Steve Schlup says. "We just didn't have enough evidence to go forward with charges and an arrest warrant at this time."
The two were going through a divorce at the time of her death.
Schlup has been following the case since it first happened.
"There in the beginning it was frustrating. It had been frustrating up to this point and it's quite a relief," he says.
Following today's arrest, Belinda's family met with deputies at the sheriff's office.
"Now we just got to go through the process of bringing everything out and reliving it again, and that's going to be a little tough," Irwin says.
The news brought them tears but also peace of mind.
"We can get on with everything. put everything back together. Of course, nothing will ever be the same, but it will be more normal then it was before."
No bond has been set for Beisly.
Deputies are still looking for another suspect they believe is involved with the murder.
33-year-old Jeremy Maples worked for Bob on his farm.
He hasn't been heard from in three weeks and was last seen in El Dorado Springs.
If you have any information on his whereabouts you are asked to call the Vernon County Sheriff's Office.