(CNN)An American citizen was detained in Vietnam while protesting a proposed economic zone law that could clear the path for Chinese investors, his family says.
William Nguyen, 32, from Houston "was beaten and dragged into the back of a police truck" on June 10 in Ho Chi Minh City, his family said in a statement.
Nguyen, a public policy graduate student, was visiting Vietnam before his graduation from the National University of Singapore when he joined the protests.
"As an American citizen and peaceful demonstrator, Will is entitled to be treated fairly, without fear of bodily and psychological harm," his family said. "He has the right to legal representation in accordance with international laws."
Video footage from the protests shows Nguyen, who had blood on his face, being dragged by a group of men down a street. The video also shows him standing up on the bed of a police pick-up truck.
Police issued a prosecution order Friday accusing him of disturbing the social order, the state-run Vietnam News Agency reported.
Nguyen was arrested after he asked officers to move police vehicles blocking the crowd's path, authorities said.
When "his request was not met," Nguyen climbed on a police car urging others to cross through, VNA reported.
The protests erupted last weekend in response to a proposed bill that would allow long-term land leases for foreign investors. The move created unease in Vietnam, fueling fears that the proposed law would give China entrenched control of some Vietnamese territory.
Nguyen was among dozens of protesters detained during demonstrations, according to Human Rights Watch.
The rights group issued a statement, asking the Vietnamese government to investigate the police response to the protests.
"People should be protected in holding demonstrations, especially around issues of great public interest," said Brad Adams, Asia director at Human Rights Watch. "But with Vietnam's poor record of handling protests, there's every reason to believe that police are punishing dissent, not simply keeping public order."
Nguyen tweeted photos of the crowds during the demonstrations and police clashes with protesters.
Nguyen is "deeply passionate about Vietnamese socio-economic issues" and has a bachelor's degree in Southeast Asian Studies from Yale University, his family said.
Lawmakers join family's efforts
Several lawmakers in Capitol Hill are calling on the Vietnamese government to release Nguyen from detention after requests from his family.
California Democrats Rep. Lou Correa, Rep. Alan Lowenthal and Rep. Jimmy Gomez said they are concerned about the student's arrest and imprisonment.
"Our next step will be to contact President Trump and Secretary of State Mike Pompeo to express the need for immediate action at the highest levels to achieve William's release. We will also be communicating our concerns and expectations over the treatment of William to the Vietnamese ambassador to the US," the Congressmen said in a joint statement.
On Saturday, US Embassy officials in Vietnam met with Nguyen for the first time since was arrested in Ho Chi Minh City -- the country's largest city once known as Saigon.
He was in "decent spirits" and was recovering from a head wound and some bruises, his sister, Victoria Nguyen, said.
"We just want him to come home. Everybody is pushing for him to come home, be released, and be done with it, but it's not going to be that easy," his sister told CNN affiliate KTRK.