LEFT: Freddie Gray. RIGHT: Officer William G. Porter (LEFT: Family photo; RIGHT: Courtesy of Helena Porter)

Who was Freddie Gray?

Freddie Gray, whose death touched off riots in Baltimore and led to charges against six police officers, went by the nickname “Pepper.”

Gray, 25, grew up in the impoverished neighborhood of Sandtown-Winchester on Baltimore’s west side.

In 2008, a lead-paint lawsuit was filed on behalf of Gray and two of his sisters against the owners of the home in which they grew up. Court papers described his difficult upbringing: a disabled mother addicted to heroin who, in a deposition, said she could not read; walls and windowsills containing enough lead to poison the children and leave them incapable of leading functional lives; a young man who was four grade levels behind in reading.

The family of Freddie Gray is urging the public to remain "calm and patient" after a mistrial is declared in the case of Baltimore police officer William Porter. (Reuters)

Such lawsuits are so common in Gray’s neighborhood that the resulting settlement payments — which Gray lived off of — are known as “lead checks.”

Close friends of Gray, who was 5-foot-8 and 145 pounds, described him as loyal and warm, humorous and happy. “Every time you saw him, you just smiled because you knew you were going to have a good day,” said Angela Gardner, 22, who had dated him off and on over the previous two years.

But Gray also had frequent run-ins with the law.

Court records show he was arrested more than a dozen times and had a handful of convictions, mostly on charges of selling or possessing heroin or marijuana. His longest stint behind bars was about two years.

How did he die?

Gray died of a severe spinal injury on April 19, one week after being arrested by police following a foot chase in his neighborhood. It was not clear why he ran when he saw the police. The officers said they found a switchblade in his pocket.

Video shot by a bystander showed officers dragging Gray into a police van after he was handcuffed.

Prosecutors said he suffered a severe spinal injury while being transported in the back of a police van, without a seat belt but with his hands and feet shackled.

Though it remains unclear precisely how Gray was hurt, medical experts on both sides of the case compared his injury to those sustained when someone dives into too-shallow water.

Six Baltimore police officers have been charged in connection with his death, including William G. Porter, whose trial on involuntary-manslaughter and other charges ended in a hung jury Wednesday. The five other officers have yet to face a jury.

In Porter’s trial, a jury of what appeared to be seven black and five white members heard two weeks of passionate legal arguments and contradictory witness testimony. In a statement, Gray’s family said they had been told Porter would be prosecuted again.

Billy Murphy, the family’s attorney, said Wednesday that mistrials were not unusual and, in most cases, a verdict is reached in a subsequent trial.

“The people who say this is not justice don’t understand how the justice system works,” Murphy said.

Gray’s family wants to avoid a repeat of the rioting that gripped the city earlier this year.

Why is there so much anger?

The violent, fiery riots that consumed Baltimore in April began as peaceful protests of what activists say is a much larger national issue: police mistreatment of black men.

Police-involved deaths have included Michael Brown in Ferguson, Mo., Tamir Rice in Cleveland, Eric Garner on Staten Island and Walter Scott in North Charleston, S.C.

Those tensions were only heightened in West Baltimore, where relations between residents and police have long been strained. A lengthy and largely peaceful march of about 1,000 people ended with flashes of violence outside Camden Yards.

But the city spiraled into chaos on April 27 in the hours after Gray’s funeral. Rioters set cars ablaze, looted businesses and injured more than a dozen officers.

Now the city is on edge again after Judge Barry G. Williams declared a mistrial in the case against Porter. As news spread outside the courthouse, a small crowd of protesters immediately expressed their frustration.

“They just declared a mistrial! That means justice has not been found!” Kwame Rose shouted into a bull horn, adding soon after, “Do not tell us to protest in peace.”

“Indict! Convict! Send those killer cops to jail!” a crowd of about two dozen chanted.

What happens next?

The next scheduled trial is for the driver of the police van, Officer Caesar R. Goodson Jr., who is set for court Jan. 6. It was not immediately clear whether the Porter mistrial would affect the scheduling of the remaining five cases.

Goodson faces the most serious charges in the case: second-degree murder, manslaughter, second-degree assault, misconduct in office and reckless endangerment.

Judge Williams is expected to meet Thursday with prosecutors and Porter’s defense attorneys to discuss a new trial date, the court announced.