Relatives of an eight-year-old Haitian boy who was taken into custody by federal immigration authorities in California are unable to locate the child, according to a Democratic lawmaker who described the case as “despicable”.

Video obtained by NBC News shows the boy being led away by three armed officials after he was summoned to what his family said was a routine immigration appointment in San Diego on 4 November.

Juan Vargas, a California Democratic congressman, told NBC on Monday that the third-grader’s whereabouts are unknown – and that he was working to try to reunite him with loved ones.

“Targeting a child, taking them away from their community and classmates, and forcing them into detention is despicable. It is inhumane,” Vargas told the network’s San Diego news affiliate KNSD.

The Haitian Bridge Alliance, an immigration advocacy group, said the boy, who attends the city’s Fay elementary school, was in the care of his uncle and cousins after his father was deported last year.

Guerline Jozef, the group’s executive director, told NBC she learned he was taken into custody after the uncle took him to the appointment, then later transferred to the office of refugee resettlement (ORR), a government agency under the direction of the health and human services department.

A spokesperson for the homeland security department said Immigration and Customs Enforcement (ICE) took the child into custody “out of an abundance of caution and to ensure the child’s safety”.

The uncle, the spokesperson said in a statement to the Guardian, was unable to prove legal guardianship – and that officials were obliged by federal anti-trafficking laws to take the boy into care as an “unaccompanied alien child”.

“Allegations that ICE took a third grader into custody to be placed in detention are false, and any suggestion otherwise is a depraved attempt to smear our ICE law enforcement officers and undermine the work of President Trump and [DHS] Secretary [Markwayne] Mullin to protect children,” the statement said.

It added that the boy lacked legal immigration status and was brought to the US by his father, who was then deported to Mexico by Customs and Border Protection (CBP), another federal immigration enforcement agency.

Jozef told NBC that the father’s abrupt deportation meant there was no opportunity to transfer formal legal guardianship to relatives of the boy in the US.

“His father has already been taken from him and deported, now this administration has stripped him of the stability, family, and community every child deserves,” she said. “I’m sure he is fearful, he is traumatized.”

Community leaders, including the board and superintendent of the San Diego unified school district (SDUSD), wrote to ICE expressing concern about the Trump administration’s decision to revoke temporary protected status (TPS) safeguards for Haitians in the US and its impact on families.

“ICE understands that this is absolutely not where this child should be,” Cody Petterson, a trustee of SDUSD, told NBC.

“For us, it’s a very clear case in which there’s no question that the best place for this child is with their caregiver, their uncle, and one of the worst places they could possibly be is in a cage somewhere with nobody they know, not understanding the process, and not understanding what’s about to happen to them.”

Jozef said the Haitian community was living “under a cloud of terror”, and that the loss of TPS protections was “incredibly painful” for families who had built lives in the US.

“The moment they kidnap or take a person within the community, we don’t know if we will ever hear from them again,” she said.

In an interview on Sunday, Donald Trump conceded that the mass deportation policy he pursued during his second presidency has been “too tough” for many people – and had contributed to the Republican party’s stinging losses in the 3 November midterm elections.

The US president acknowledged in an interview with CBS’s 60 Minutes that aggressive immigration enforcement actions had “both helped and hurt” – and hinted at a softer approach for his remaining two years in office.