It was a dispute over $200 in rent, a landlord-tenant disagreement that probably happens all the time in New York.

But this one had a grim climax that was captured in a startling video — the landlord dead, his tenant accused of killing him, a violent end to a story that began as one immigrant trying to help another.

Edgar Moncayo, 71, and Alex Garces, 22, both arrived in Queens from Ecuador, though several decades apart, looking for work. Both struggled to make ends meet — Mr. Moncayo was a valet at two parking lots and Mr. Garces was an undocumented laborer working construction.

In December, Mr. Moncayo rented a small room in his modest East Elmhurst home to Mr. Garces, who arrived from Ambato, Ecuador, three years ago.