Call it vocal support. I myself am not sure what power a mayor has in criminal prosecution besides apparently making some decisions about policing.

Adams stressed that he is barred from directing commands to local prosecutors, and refrained from explicitly weighing in on the charges Alba was slapped with and amount of bail set. The mayor, however, does oversee the NYPD, which also charged the clerk with murder.
“The DA has his job, I have my job as the mayor of the city of New York, as the mayor of the city of New York, I support hard-working, innocent people that are doing their job, and I saw him as a hard-working innocent New Yorker that a person went behind the counter and attacked,” said Adams, a retired NYPD captain.