(CNN) -- The parents of Otto Warmbier filed a wrongful death lawsuit against the North Korean government on Thursday charging that the country's regime tortured and killed their son, according to lawyers for the family.
Warmbier -- the 22-year-old American student who was detained in North Korea for 17 months -- was returned to his family "with severe brain damage and in a nonresponsive state" in June 2017.
He died on June 19, 2017.
"Otto was taken hostage, kept as a prisoner for political purposes, used as a pawn and singled out for exceptionally harsh and brutal treatment by Kim Jong Un," Otto's father, Fred Warmbier, said in a statement.
"Kim and his regime have portrayed themselves as innocent, while they intentionally destroyed our son's life. This lawsuit is another step in holding North Korea accountable for its barbaric treatment of Otto and our family," the statement said.
The suit comes at a sensitive moment for US-North Korean relations, with President Donald Trump due to meet face-to-face with the North Korean leader in the coming weeks.
In the lawsuit, Warmbier's attorneys outline how escalating tensions between the Obama and Trump administrations and North Korea coincided with Warmbier's detention. Congress passed banking sanctions in response to Warmbier's death late last year, and Trump re-designated the country as a sponsor of terrorism in November, which allowed the Warmbiers to sue the foreign government.
Since then, the relationship between North Korea and the US appear to have warmed. On Thursday, the White House released photos of now-Secretary of State Mike Pompeo shaking hands with Kim, who traveled to visit North Korea for a secret meeting a month ago while he was still CIA Director.
Warmbier has spoken to CNN about his son's detainment and death, saying Otto was "on his deathbed" when he returned to the United States.
"Otto was systematically tortured and intentionally injured by Kim Jong [Un] ... Kim, and his regime. This was no accident," he told CNN in September.
Warmbier was taken into custody by North Korean authorities during a five day sightseeing tour of the reclusive state, who accused him of stealing a political poster from a restricted floor on his hotel.
He was sentenced to 15 years of hard labor.
When Otto arrived back in the US he was in a persistent vegetative state but North Korea claimed he had contracted botulism while in prison.
The Hamilton County Coroner's office in Ohio released a report in September outlining the findings of an external examination of Warmbier's body.
That report described a 4.3 inch-by-1.6 inch scar on Warmbier's right foot as well as a number of smaller scars, but did not contain details as to what caused them or how long they had been there.
The coroner's report lists the cause of death as "undetermined" -- an "unknown insult more than a year prior to death" and the complications of his brain injury.
Warmbier's parents declined a full autopsy.
"The family's objection to an autopsy was honored, and only an external examination was performed," the coroner's office said in a statement last June.
The lawsuit filed Thursday describes in detail their encounter with their son when he landed in Cincinnati after his medical evacuation from North Korea. The parents noticed he was blind, deaf, had a shaved head and a feeding tube, "was jerking violently and howling" and had misaligned teeth, the lawsuit says.
In addition to wrongful death, they claim North Korea inflicted emotional distress on them through the assault and battery of their son. The parents are asking for compensation for their pain and suffering, among other claims.
A North Korean Foreign Ministry spokesman denied that Warmbier was tortured while in North Korean custody, according to a September report by the country's state-run news agency KCNA.
But questions have continued to swirl around how this happened -- and specifically, what happened to Warmbier while he was in North Korean custody.