The three men fled empty-handed, authorities said.
Dalton said they were arrested Monday, but he did not say where.
Bail was set at $1 million for Hodge and $750,000 each for Williams and Pierce, officials said.
Singh, an immigrant from India, usually worked the second shift until 10 p.m. His brother, Satinder, also worked at the station.
"This is a great arrest, not only for the Singh family, but also for the city of Woodbury," Dalton told reporters at the prosecutor's office.
Records show that Williams was released from state prison Aug. 20 on drug and theft charges, Pierce has convictions for resisting arrest and drug possession, and Hodge has a conviction for criminal restraint.
Dalton said all units of his office, including the major crimes, cyber crimes, and fugitive units, were involved in the investigation. He did not detail their roles.
Dalton said it was not one tip that helped crack the case, but rather "the culmination of good police work."
Satinder Singh, 35, thanked the officers who arrested "the bad guys" and the "whole city" for supporting his family.
Dalton said his office offered $5,000 toward a reward; Woodbury police offered $3,000, and $2,000 in donations flowed in. No decision had been made on paying the reward, he said.
Surinder Singh had worked at the station on and off for at least 10 years, according to owner Arjun Goyal.
Goyal said just after the killing that the station had been robbed two or three times in 10 years.
Singh immigrated from Ludhiana, in India's Punjab state, about 15 years ago and lived in Woodbury with his mother and extended family.
He was the father of two girls, ages 2, and 9 months. His widow, Kirandeep, is in India with their children to see her parents, but the family will return, Satinder Singh said.
Satinder Singh said he had called his sister-in-law earlier Tuesday to let her know about the arrests, he said.
"She was very happy the bad guys got caught," he said.
The gas station reopened two weeks after the killing, Reddy Rathnaker, a co-owner, said Tuesday. He said the owners now plan to install surveillance cameras.
Satinder Singh said he was too scared to work there again.