"Hawaii Five-0" star Alex O’Loughlin joined hundreds in hitting the pavement Saturday for the 2nd Annual Hawaii Walk to Defeat ALS at Kapiolani Park.

In an interview Wednesday, the actor known to the world as Steve McGarrett said he had personal reasons for supporting the fundraising event.

"My wife’s mother passed from ALS. My kids don’t have a grandmother because of this disease. My wife doesn’t have a mother, and I don’t have a mother-in-law," said O’Loughlin, who is married to surfer/model Malia Jones. The couple have three children.

ALS, amyotrophic lateral sclerosis, also known as Lou Gehrig’s disease, attacks nerve cells and pathways in the brain and spinal cord. As it progresses, ALS patients lose the ability to move and speak, and eventually cannot swallow or breathe on their own. In most cases their mind and senses continue to function normally.

"To watch what it does to families and watch someone die in such a horrible way with no chance of a cure …" O’Loughlin’s voice trailed off for a moment. "That’s the thing about this disease; there’s not even a ‘chemo’ of sorts. There’s just no hope, and I pray as we all do, that one day if we raise enough money and put enough energy and time into that we will find something for people who are suffering from ALS."

The cause of ALS is unknown and it does not appear to be inherited.

"It’s just out of the blue," O’Loughlin said. "My wife’s mother was a triathlon runner. It’s a great and cruel riddle."

O’Loughlin is one of many celebrities to support ALS research by participating in the ice bucket challenge, a grass-roots fundraiser and awareness campaign that has gone viral thanks to video posts by participants worldwide.

The challenge involves taking a video of someone dumping a bucket of ice water over your head — or dumping it on yourself — and posting the video on social media then calling on someone else to do the same.

O’Loughlin was challenged by "Five-0" writer/producer Peter Lenkov and enlisted fellow cast members Daniel Dae Kim and Jorge Garcia to do it with him.

"We called out the president of CBS, Les Moonves — a number of people called him out — and he graciously and heroically accepted the challenge. We thought we were sort of taking it to another level using big Gatorade-size ice buckets, but we’ve since looked at a whole bunch of (videos) and there are some pretty impressive ones out there," O’Loughlin said.

"I’ve seen so many high-profile people getting in on this, and the best part is that it’s a fun way to do it and everyone’s kind of challenging each other, but it’s really stirring up a lot more awareness of ALS."

Regarding season five of "Hawaii Five-0," O’Loughlin wouldn’t go into specifics regarding what awaits McGarrett but it sounds like fans can expect some surprises. Hawaii will get a sneak peak at the season premiere at a Sunset on the Beach screening in Waikiki on Saturday.

"There have been some shifts with the team. There’s been some new additions. There’s some characters we’ve had to say goodbye to but the core team is still there," he said. "McGarrett still battles with the loss of his mother (and) we’re going to be exploring some new stuff about his father and that loss. It’s a big season opener. We’re certain you’re not going to be disappointed, and we’re looking forward to seeing everybody on the beach next week."

For more information about ALS, visit www.ALS-Hawaii.org.