This plot is straight out of a "Columbo" episode "An Exercise in Fatality" (1974).
Milo Janus owns a chain of health clubs, but one of his franchisees discovers the man is cheating him - and can prove it to the authorities. Janus responds by murdering his partner and making it look as if he had accidentally killed himself trying to lift a barbell that was too heavy for him.
Is that the one where a giant electromagnet was used from the apartment below?
This murder method was also featured in an episode of Forensic Files. A man murdered his wife by crushing her throat with a weight and told police it had fallen on her.