MESA, Ariz. -- The Mesa Police Department proudly touts the dramatic reduction in crime since Chief George Gascon took over the department three years ago.

“We have had one of the biggest crime reductions of any city in the area -- rates back to late 60’s levels,” said Gascon.

But what thrust him into the national spotlight was his very public stance against Sheriff Joe Arpaio and Arpaio’s controversial immigration sweeps, one of which targeted Mesa's city buildings last October.

"When you start assuming that people are here illegally because of how they look, or the way they speak, or the way they dress, we're really going in the wrong direction,” said Gascon.

Gascon admits he struggled with how to handle the immigration issue, a political hot potato.

“You have to be able to look at yourself in the mirror every morning -- and that's always been my test. Do I feel internally good? Do I feel I'm doing the ethical, legal and moral thing? If the answer is yes, I'm going to do what it takes to get there," said Gascon. "I was conflicted in how do I educate on how to get people to understand that policing can not violate those basic tenets of the law."

He carefully avoided answering a question about whether Arpaio’s tactics broke the law.

"You know, I'm going to reserve my opinion because I think it would be inappropriate. I know there are investigations ongoing,” answered Gascon.

A Cuban immigrant, Gascon is widely credited for giving the Valley's Latino community a stronger voice. Many called his departure “a huge loss,” and said they’re losing an advocate.

The outgoing Mesa police chief says the biggest challenge for the next chief will undoubtedly be money.

“I think the biggest challenge the next couple of years is going to be financial,” said Gascon. “If we continue in the direction we're going with the reduction of personnel, this organization by this time next year could be significantly impacted by reduction in personnel. That’s going to require a very skillful allocation of resources.”

After weeks of speculation, Gascon announced last week he accepted the job as San Francisco's top cop. His last day in Mesa will be July 31.

Mesa’s city manager has met with all three of the police department’s assistant chiefs, and is in the process of naming an interim chief.

The assistant chiefs include Mike Denney, who serves as chief of staff; Mike Dvorak, who oversees support services; and John Meza, chief of operations.

Gascon would not say whether he had a recommendation as to who should succeed him, but did express confidence in the abilities of all three assistant chiefs.

“The decision will be made in the near future,” said city of Mesa spokesman Steve Wright.