While many celebrities were out partying over Halloween weekend in Los Angeles, Jason Momoa went back home to Hawaii for a very good cause.

The 43-year-old actor appeared at an event at Brigham Young University – Hawaii on Friday, to promote people registering for the bone marrow registry.

He did this on behalf of his longtime friend Travis Snyder, who suffers from leukemia, and a six-year-old boy named Rhyder Lopez, who was born with the ultra-rare genetic disease Hemophagocytic lymphohistiocytosis (HLH).

Good cause: While many celebrities were out partying over Halloween weekend in Los Angeles, Jason Momoa went back home to Hawaii for a very good cause

Momoa took to his Instagram over the weekend to share videos from the event and to get his 17.2 million followers to get involved with his Be The Match campaign.

Momoa sent the first video on Friday, which showed the massive actor rolling up to campus on a motorcycle to cheering fans, while he met young Rhyder Lopez.

‘Mahalo Nui to @byuhawaii for hosting @bethematch it was amazing meeting everyone in Laie yesterday, mahalo to everyone who came to get swabbed,’ Momoa said in the caption.

Rhyder: He did this on behalf of his longtime friend Travis Snyder, who suffers from leukemia, and a six-year-old boy named Rhyder Lopez (left), who was born with the ultra rare genetic disease Hemophagocytic lymphohistiocytosis (HLH)

Involved: Momoa took to his Instagram over the weekend to share videos from the event and to get his 17.2 million followers to get involved with his Be The Match campaign

Meeting Rhyder: Momoa sent the first video on Friday, which showed the massive actor rolling up to campus on a motorcycle to cheering fans, while he met young Rhyder Lopez

‘Hopefully one step closer to finding a match for Rhyder Lopez & @thetravissnyder, please! Go to link in bio and my story to learn more on how you could help be a super hero and save lives. Join the registry ! Please do your part and make a difference and help! Aloha j’ he concluded.

The video also showed Jason and Rhyder getting leis while a haka was performed for them, before meeting Rhyder’s family and signing a number of autographs.

He also went out to meet his fans and thanked them for coming, adding he would take a picture with anyone who got swabbed to try and, ‘be the match.’

Autographs: The video also showed Jason and Rhyder getting leis while a haka was performed for them, before meeting Rhyder’s family and signing a number of autographs

Fans: He also went out to meet his fans and thanked them for coming, adding he would take a picture with anyone who got swabbed to try and, ‘be the match’

‘I get emotional when I think about it. If it’s my kids or your kids… it doesn’t take much. You just got to swab a cheek, and you can save some lives,’ Momoa said.

‘From the bottom of my heart, thank you for coming. I love you, Aloha!’ he said to the group.

He was also seen hanging out while two fans got swabbed as they mentioned how easy the whole process was, showing them swabbing the inside of their cheek with a cotton swab.

Emotional: ‘I get emotional when I think about it. If it’s my kids or your kids… it doesn’t take much. You just got to swab a cheek, and you can save some lives,’ Momoa said

Swab: He was also seen hanging out while two fans got swabbed as they mentioned how easy the whole process was, showing them swabbing the inside of their cheek with a cotton swab

Momoa also reposted BYU Hawaii’s video from the event that was posted on Sunday, thanking everyone again for coming out to support his worthy cause.

‘Mahalo again for everyone that took part and came down to BYU ! Please make a difference save a life, join the registry link in bio! Aloha j’ Momoa said.

Momoa’s friend Snyder has been battling acute myeloid leukemia since 2015, and finding a matching bone marrow donor is more complicated than just matching blood types.

Thanks: Momoa also reposted BYU Hawaii’s video from the event that was posted on Sunday, thanking everyone again for coming out to support his worthy cause

Complicated: Momoa’s friend Snyder has been battling acute myeloid leukemia since 2015, and finding a matching bone marrow donor is more complicated than just matching blood types

A person’s ethnicity is a key factor, with Momoa revealing in the video that, even though Snyder is, ‘the whitest guy I know,’ he does have some Polynesian heritage, which is part of why the weekend event was so important.

As for young Rhyder Lopez, both he and his 9-year-old brother named Rhaiden were born with HLH, though Rhaiden found a matching donor seven years ago while Rhyder is still waiting for his blood stem cell match.

Fans can visit BeTheMatch.org/ForTravis to learn more about his story.

Polynesian: A person’s ethnicity is a key factor, with Momoa revealing in the video that, even though Snyder is, ‘the whitest guy I know,’ he does have some Polynesian heritage, which is part of why the weekend event was so important