Just days after the body of Fahim Saleh, a successful tech entrepreneur, was found dismembered in his luxury condominium in Manhattan in July 2020, his former personal assistant, Tyrese Haspil, made a series of unsettling web searches.

“Fahim Saleh.” “Murder of tech C.E.O. in New York.” “Dismembered body.”

The search queries were just some of the chilling details that emerged during Mr. Haspil’s murder trial this month in Manhattan Criminal Court. And on Monday jurors convicted him of stealing hundreds of thousands of dollars from Mr. Saleh — and then killing him and cutting up his body in an effort to conceal what he had done.

Mr. Haspil, 25, of Brooklyn is expected to be sentenced on Sept. 10.

“Tyrese Haspil tragically cut Mr. Saleh’s life short — a man who came from a close-knit immigrant family and followed his passions to become a successful entrepreneur,” said Alvin L. Bragg, the Manhattan district attorney, in a statement announcing the conviction on Monday. “I hope the accountability delivered by today’s verdict can provide a measure of comfort to Mr. Saleh’s loved ones as they continue to mourn his loss.”

Mr. Saleh, 33, was born in Saudi Arabia to Bangladeshi parents and grew up in Poughkeepsie, N.Y. He was the founder of two motorcycle ride-sharing companies, based in Bangladesh and Nigeria, the latter of which raised millions in venture capital. After his death, he was remembered as an innovative businessman and a generous friend.

Sam Roberts, Mr. Haspil’s lawyer, said on Monday that he was disappointed by the verdict. He acknowledged that Mr. Haspil had committed the crime and said the killer felt remorse. “We fully believe that Tyrese Haspil is not solely and only the worst thing that he’s done in his life,” he said. “We hope that the court will understand that there are mitigating factors here.”

Mr. Haspil’s ill-fated scheme began in the fall of 2018, when he was working as Mr. Saleh’s entrepreneurial assistant and began stealing money from his companies to purchase lavish gifts for his new girlfriend.

By December, Mr. Haspil had created a bogus corporate entity and bank account into which he funneled more money.

In May 2019, fearing he would be discovered, Mr. Haspil resigned from his position as Mr. Saleh’s assistant, though he continued to steal money in increasingly large amounts even after his departure, prosecutors said.

Sure enough, in January 2020, Mr. Haspil’s scheme was detected. Mr. Saleh confronted Mr. Haspil over a $35,000 debt, prosecutors said, and offered to settle it with a two-year repayment plan, instead of bringing criminal charges against him.

Mr. Haspil agreed. But Mr. Saleh did not know that Mr. Haspil had stolen far more from him in a different scheme, involving a fraudulent PayPal account. Mr. Haspil began paying him back with those stolen funds even as he continued operating that scheme, eventually amassing about $400,000 in stolen funds, prosecutors said.

Concerned that his more lucrative theft would also be discovered, Mr. Haspil began plotting to kill Mr. Saleh to prevent him from testifying against him in any criminal proceedings, prosecutors said.

What followed was a meticulously researched and executed killing that some investigators theorized at the time had been planned by Mr. Haspil to look like a professional assassination.

Mr. Haspil spent weeks researching the technology, weapons and cleaning supplies needed to carry out and cover up a homicide, prosecutors said. He purchased clothing to conceal his identity, and he tracked Mr. Saleh’s whereabouts on social media in preparation.

That May, Mr. Haspil decided to murder Mr. Saleh in his home and made two more web searches — for the anatomy of the human neck, and for Mr. Saleh’s building plans. In June, he purchased contractor-grade trash bags, a Swiffer floor cleaning tool and a saw.

Then, early in the morning of July 13, Mr. Haspil entered Mr. Saleh’s Manhattan apartment building wearing a black suit and an opaque face mask. He followed Mr. Saleh into an elevator, which opened directly into his apartment, subdued him with a Taser and fatally stabbed him.

He left the apartment and returned the following day to dismember Mr. Saleh’s body with an electric saw, but left again to purchase a battery charger. While he was out, Mr. Saleh’s cousin went to check on him and discovered the scene.

Mr. Haspil was arrested four days after the murder at an Airbnb he had booked for his girlfriend’s birthday celebration.