The leading Democratic presidential candidates are calling for police reform and racial justice following the death of an African-American woman after a controversial arrest.

"My heart breaks at seeing another young African American life lost too soon. Sandra Bland had a bright future ahead of her and it is particularly tragic that she lost her life just as she was to start her new career," front-runner Hillary Clinton said in a statement on Wednesday.

Bland is the woman whose arrest was captured on video. After a routine traffic stop led to a confrontation with the police officer, she was taken into custody. She died in jail three days later due to an apparent hanging. Her death is under investigation.

Bernie Sanders and Martin O'Malley were both challenged by Black Lives Matter activists at a liberal conference this weekend. They both condemned the police officer's actions in the Bland case.

"This video of the arrest of Sandra Bland shows totally outrageous police behavior," Sander said in a statement. "No one should be yanked from her car, thrown to the ground, assaulted and arrested for a minor traffic stop. The result is that three days later she is dead in her jail cell."

Sanders added, "This video highlights once again why we need real police reform. People should not die for a minor traffic infraction. This type of police abuse has become an all-too-common occurrence for people of color and it must stop."

Martin O'Malley, who was criticized for saying "All lives matter" at the Netroots Nation conference in Phoenix, Ariz., issued a similar statement.

"My heart breaks for Sandra Bland and her family," O'Malley said. "This is a horrible loss of life that demands a full, thorough and independent investigation of the traffic stop, the arrest and Ms. Bland's tragic death in custody."

"From what I've seen, the circumstances of this case are incredibly disturbing," Clinton added. "I hope and expect that there will be a full investigation into this situation. It is also a tragic reminder of the ongoing systemic issues of race and justice in America that we must address with urgency, and we have to do more than talk — we have to take action."