BANGKOK--Four Thai police officers charged with murder in connection with the deadly shakedown of a suspected drug dealer in custody were arrested Wednesday after a video clip of the incident shared on social media caused a public furor.

Three other officers were still being sought in connection with the Aug. 5 incident at their police station in the province of Nakhon Sawan, north of Bangkok, said police Col. Kissana Phathanacharoen, deputy national police spokesman. They include a police colonel with the nickname “Jo Ferrari” because of his collection of expensive sports cars, Thai media reported.

Allegations of police brutality and corruption are not rare in Thailand, but the leaked video showing the suspected drug dealer suffocating after officers placed plastic bags over his head in an alleged extortion effort and an initial dilatory investigation stoked outrage.

Police have also come under harsh criticism recently for their use of force in trying to quell anti-government street protests in Bangkok. While some demonstrators employ violent tactics, police have been accused of overreacting and using dangerous methods of crowd control, including firing rubber bullets at close range.

“This case of police torture and murder is shocking. But this is not the first case and it is unlikely to be the last case until and unless the police conduct serious interrogations and investigations and leave no stones unturned,” said Sunai Phasuk, a senior researcher for Human Rights Watch.

Police started investigating the case only after a well-known lawyer, Decha Kittiwittayanan, published an account of it on his Facebook page.

Decha said he had received a complaint from a junior policeman in Nakhon Sawan who said that police had arrested two drug suspects, a 24-year-old man and his female companion, with over 100,000 methamphetamine tablets.

The policemen first demanded 1 million baht ($30,560) from the suspects, which they agreed to pay for their release, according to the account. But the senior officer at the scene, police Col. Thitisan Uttanapol, demanded double that amount and ordered his subordinates to cover the male suspect’s head with a plastic bag and beat him until he agreed, said the junior policeman, whose name was not revealed.

When the suspect died, Thitisan allegedly ordered his men to take the body to the hospital and tell the doctor the death was caused by a drug overdose. The junior policeman said the woman was released but told not to say anything about it, and that Thitisan paid the victim’s father to remain silent.

The initial police response to the furor over the story posted by the lawyer was to transfer Thitisan to another post.

On Tuesday, however, a video clip of the incident was shared on the Facebook page of another lawyer, Sittra Biabanggerd, who said he had received it from a police officer at the Nakhon Sawan station.

It shows the male suspect in handcuffs being led into a room, his head covered with a black plastic bag. He is then assaulted and thrown to the floor by officers who put more bags on his head. One of them appears to briefly kneel on him. The man, identified by Thai media as Jeerapong Thanapat, then goes limp. Police try in vain to revive him with a jug of water and CPR.

“We are proceeding with this case, pursuing both criminal cases and disciplinary action,” police spokesman Kissana said Wednesday.

Small-scale corruption, such as soliciting bribes from motorists, is not rare among poorly paid police officers. Some also have a reputation for beating suspects to elicit confessions

But cases occasionally emerge of corruption at a higher level. A case known as the “Blue Diamond Affair,” involving the 1989 theft of jewelry by a Thai overseas worker from the palace of a Saudi prince, cast a harsh spotlight on the police force after much of the loot went unrecovered and a police general was convicted of kidnapping and killing relatives of a witness in the case.

Human Rights Watch’s Sunai charged that Thai police often act with total impunity, protecting each other.

“This is no longer an individual issue. It’s a corrupt system that allows abusive acts,” he said.