Tom Sullivan announces his state Senate bid on Tuesday, Feb 23, 2016 in Centennial, Colo. His son, Alex, died in the Aurora theater shooting.

(Vic Vela/CPR News)

The father of a young man who died in the 2012 Aurora theater shooting announced his bid for a Colorado state Senate seat on Tuesday.

Tom Sullivan of Centennial fought back tears when he talked about how his son Alex – who died on his 27th birthday – is still with him in spirit as he prepares for the race.

“I would certainly hope that the actions that I take, I continue to do to try to make him proud of me,” Sullivan said at press conference inside Greenwood Village’s Silo Park.

Alex was one of 12 people who were killed by James Holmes on the night July 20, 2012. Holmes was convicted last year and sentenced to a life behind bars.

Since his son’s death, Sullivan, a Democrat, has become a vocal advocate of gun control. He’s testified at the state Capitol in support of measures to expand background checks on gun sales.

Sullivan also recently testified in support of a Republican-sponsored bill that would have allowed juries to reach a death sentence, even if there were one holdout.

Sullivan had hoped Holmes would receive the death penalty, although the entire jury did not agree.

Sullivan will be taking on Republican Sen. Jack Tate, who was selected by a Republican Senate District 27 vacancy committee in December to fill the seat of former Sen. David Balmer. Balmer resigned last year after accepting a new job.

At the press conference, Sullivan took aim at Tate’s conservative beliefs.

“If you side with your own party, over the people of Arapahoe County and the overwhelming number of people of Colorado who support background checks on gun purchases, you are too extreme and out of touch to serve here,” Sullivan said.

Sullivan faces an uphill climb in a Republican-leaning district. He said he feels he has a chance to win in a presidential election year, when more Democrats -- and more voters in general -- are expected to go the polls.