Baltimore lost its third police commissioner in three years on Tuesday, the latest blow to the city’s efforts to come to grips with a host of serious problems, including the nation’s highest big-city murder rate; a shocking corruption scandal; abusive police practices documented in a Justice Department investigation; and the lingering aftermath of the death of Freddie Gray.

The commissioner, Darryl De Sousa, 53, a career Baltimore officer, had been in the post for just four months. He resigned after being charged by federal prosecutors in Maryland with willfully failing to file income tax returns for 2013, 2014 and 2015. The charges are misdemeanors, with a maximum sentence of up to one year in prison and a $25,000 fine for each of the three counts.

When the matter first came to light last week, the mayor of Baltimore, Catherine Pugh, backed Mr. De Sousa, who acknowledged that he had failed to file the returns but said he had paid his taxes through withholding. He said there was “no excuse” for failing to file, and attributed what he had done to failing to “sufficiently prioritize my personal affairs.”

But a day later, after others in the community expressed serious concerns about having the city’s police force led by someone under the cloud of federal charges, the mayor suspended him.