OCEANSIDE, Calif. -- The gun that former San Diego Chargers linebacker Junior Seau used to shoot himself in the chest was not registered to him, investigators said Friday.

Detectives are still trying to determine who owns the gun, Oceanside police Lt. Leonard Mata told Fox 5 News.

The San Diego County Medical Examiner's Office on Thursday confirmed that the former Chargers star killed himself with the gun. Oceanside found it on the floor near his body but no suicide note was discovered at the scene.

Chargers chaplain Shawn Mitchell told the UT San Diego that Seau's  family decided to donate his brain to science to help determine whether repeated trauma suffered by football players leads to depression. However, Seau's sister, Annette, told reporters Friday morning that the family had not yet made any such decision, nor had they come up with definite plans for a funeral or public memorials.

"Their thoughts are if they can help someone else'' by that decision, "they think good can come out of the tragedy,'' he told the newspaper.

Private and public memorial services were tentatively scheduled for May 11th and 12th at New Venture Christian Fellowship in Oceanside and Oceanside High School, respectively. The details for each were still being worked out.

A memorial paddle-out for surfers was also planned for noon this Sunday in front of Seau's home.