Four Americans kidnapped by heavily armed men in Matamoros, Mexico, had travelled there for cosmetic surgery, relatives told US media.
One of them was to have a tummy tuck – removing abdominal fat – in a border town, said the sister of one of them.
“To see a member of your family thrown in the back of a truck and dragged, it is just unbelievable,” Zalandria Brown, told AP about her brother Zindell.
A Mexican woman was killed in the incident.
The FBI has offered a $50,000 (£42,000) reward for the return of the Americans.
The other people in the group have been identified in US media as Latavia McGee, Shaeed Woodard and Eric James Williams.
They were driving through Matamoros – which is directly across the border from the Texas town of Brownsville – in a white minivan with North Carolina licence plates when unidentified gunmen opened fire, the FBI said.
Video shows them being put in a pickup truck by heavily armed men. One is manhandled onto the vehicle while others appear to be unconscious and are dragged to the truck.
Mexican President Andrés Manuel López Obrador described the incident as a “confrontation between armed groups”. He said his “entire government” was working to secure the Americans’ release.
According to an unnamed US official quoted by CNN, investigators believe a Mexican cartel probably mistook the Americans for Haitian drug smugglers. (BBC)