(CNN) -- More violence. More tear gas. No answers.
Stun grenades and tear gas canisters arced through the night sky and into crowds of protesters overnight in Ferguson, Missouri, after police said they had been targeted with rocks, Molotov cocktails and gunfire amid continuing demonstrations over the death of Michael Brown.
Two people were shot -- not by police, authorities said. Four officers were injured. Police arrested at least 31 people. Police and protesters blamed outside agitators for the gunplay and violence.
"We don't need these antagonizers out here," said protester Jerrell Bourrage, who earlier grabbed one of the bottle-hurling demonstrators and told him to stop. "We need people who can stand out here to the side and still let your word be known."
The protests are the latest spasm of violence over the shooting of Brown, an unarmed African-American teenager, by white police Officer Darren Wilson on August 9.
Meanwhile, Trayvon Martin's mother has written an open letter to the parents of Michael Brown. Sybrina Fulton's letter is published in Time Magazine, and on its website.
In it, Fulton writes that she wishes she had a word of automatic comfort, but she doesn't. She writes the Browns will hear character assassinations about Michael, and she's certain they already have. She ends her letter with a fiery call to action, writing, quote -- "if they refuse to hear us, we will make them feel us."
Trayvon Martin was fatally shot by neighborhood watch volunteer George Zimmerman in February 2012. Zimmmerman claimed he acted in self-defense, and was found not guilty of second-degree murder.