Cops are probing whether a furious customer pulled the trigger after a Chinese food delivery driver working three jobs was shot dead. Zhiwen Yan, 45, was mid-shift late on Saturday riding his scooter in Forest Hills, Queens, at 9:30 pm, cops report, when he was struck in the chest by an unidentified suspect. The shooting saw Yan and the suspect briefly exchange remarks before he was fatally hit near 108th Street and 67th Drive, in what is typically a calm, close-knit community. [tweet_embed] May 5, 2022[/tweet_embed] Police state the incident came immediately after Yan, a father-of-three who moved to New York from China more than two decades ago, completed a delivery. Shocking video obtained by police shows Yan pulling onto 108th Street when the suspect approaches on foot with a gun drawn. In the clip, which has not been released, Yan attempts to roll backward on the bike to move away when the suspect suddenly shoots, sending the scooter crashing to the ground. According to his family, the Chinese-born New Yorker had been working seven days a week when he was killed, endeavoring to support his wife and young children. Cops have yet to make an arrest in the case - and thus far, a suspect has not been named. [tweet_embed] May 5, 2022[/tweet_embed] Police are investigating claims from Yan's fellow staffer Soi Chung, 70. Chung alleges it was a 50-year-old 'disgruntled' customer who took his friend's life. According to Chung, the supposed suspect had 'multiple' disputes with the Forest Hills eatery, Chinese restaurant Great Wall and pulled a gun on staffers during a separate incident back in January. Another incident last year saw the angry patron become aggravated over the amount of duck sauce given to him in one of his orders, Chung informed The New York Post, spurring a campaign of harassment, vandalism, as well as threats from the customer. The only person of interest in the case thus far is the customer who is currently wanted for questioning by the New York Police Department, law enforcement sources told the outlet. The beef with the rowdy regular, Chung recalled, commenced one night last year. 'The customer came in and ordered some food,' Chung, who has worked at the Queens establishment for 20 years, told the paper Monday. [tweet_embed] May 5, 2022[/tweet_embed] The encounter was friendly at first, according to Chung - yet things quickly turned sour when the customer deemed the amount of duck sauce he had received with his order to be unsatisfactory. 'He left with the food but then came back and said 'It's not enough,'' Chung said. 'He came to the counter and wanted more food, more duck sauce.' An argument then ensued, Chung told the outlet, prompting Yan's and Chung's employer to get involved. 'They had an argument,' Chung told the Post, 'and the boss said, 'It's enough already.' The veteran restaurant worker recalled that that the jilted customer then sauntered out of the restaurant in a huff, before making his return to the establishment, at which point he vandalized the place with, of course, the duck sauce. 'The guy left the restaurant, and later came back and threw the duck sauce, everything, all over the place,' Chung recalled. 'The police came and took a report, but the guy was gone.' However, according to Chung, the strange saga was far from over - with the guest's harassment campaign only growing more brazen and threatening. 'After that, sometimes, he'd be waiting around outside,' Chung told the outlet Tuesday, as cops continued to comb the city in hopes of tracking down Yan's killer.