Robert De Niro’s former son-in-law had a gut-wrenching reaction arriving at the home of the actor’s daughter to mourn the unexcepted death of their 19-year-old son, Leandro De Niro Rodriguez.

Carlos Rodriguez, a pioneering subway graffiti artist, wore a baseball cap and shades but could not conceal his anguish when he showed up at Drena De Niro’s apartment building in the West Village Monday morning.

Rodriguez, dressed in a white long-sleeved shirt and jeans, and carrying a large blue duffel bag, appeared visibly distressed as he leaned against the front door and bowed his head, hiding his face from view, as seen in exclusive photos taken by The Post.

Rodriguez did not make any public statement while waiting for someone to open the door to the building and let him in.

It was Rodriguez’s first public sighting since the sudden news of his son’s death was shared by Leandro’s mom on her Instagram page early Monday.

“My beautiful sweet angel. I have loved you beyond words or description from the moment I felt you in my belly,” the 51-year-old Drena De Niro wrote of her only child.

The “Taxi Driver” star’s grandson was found dead inside his lower Manhattan apartment by a friend who had gone to check on him after not hearing from him for several days, according to a report.

The friend found Rodriguez sitting lifeless in a chair without any obvious signs of trauma, TMZ reported.

The NYC Office of Chief Medical Examiner told The Post in an email that it was investigating Rodriquez’s cause and manner of death.

Leandro’s mom, Drena, was born to Diahnne Abbott and was adopted by Robert De Niro when the couple married in 1976. They divorced in 1988.