On Thursday morning, Rev. Al Sharpton's 87-year-old mother Ada Sharpton passed away following a prolonged battle with dementia and Alzheimer's.

The news comes in the wake of another tragedy close to Al Sharpton's heart. The reverend has been deeply involved in the fight for justice on behalf of Florida teenager Trayvon Martin, who was shot and killed by George Zimmerman, the captain of a neighborhood watch group, on February 26.

Sharpton will continue campaigning for authorities to take legal action against Zimmerman, who claims that he shot the unarmed Martin in self-defense. He has yet to be arrested.

Sharpton, head of the New York City-based civil rights organization National Action Network, was incensed by the circumstances surrounding Martin's death. The fact that a young, unarmed man could be killed by a neighborhood watch captain, while his family was blatantly misled by local police as to the background of the shooter, is disturbing, he said in a statement last week.

Sharpton was invited to participate in the Martin case by attorney Benjamin Crump, who represents Trayvon's parents. Crump had previously worked with Sharpton in the 2006 case of an African-American teenager who died at a Florida boot camp.

I had to call people like Sharpton and a few other black civil rights leaders and the black media to tell them about this story,'' said Crump to the Daily Beast on Thursday. I had to get them to understand what happened to this young man and what hadn't happened in his case so they could spread the word.''

Sharpton will attend a rally for Martin and his family on Thursday night, and then will fly to Dothan, Ala., to make funeral arrangements for his mother.

Just after 6 a.m. on Thursday morning, Sharpton posted a note on Twitter: My mother, Ada Sharpton passed in the early hours of this morning. She was my all. I hope God will give her now, PEACE. I love you, Mom.

Minutes later, he added: I am on the flight to Florida and will move forward with our plans to protest the killing of Trayvon Martin. My MOM would have wanted me to.

Sharpton is headlining at the rally at Mellon Park in Sanford, Fla., at 7 p.m. on Thursday night. Thousands of attendees are expected.