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Protesters plan to 'shut down' Baltimore as questions remain unanswered about Freddie Gray

  • Baltimore Police Department Commissioner Anthony Batts speaks about the investigation into Freddie Gray's death at a news conference, Friday, April 24, 2015, in Baltimore. Gray died from spinal injuries about a week after he was arrested and transported in a police van. (AP Photo/Patrick Semansky)

    Baltimore Police Department Commissioner Anthony Batts speaks about the investigation into Freddie Gray's death at a news conference, Friday, April 24, 2015, in Baltimore. Gray died from spinal injuries about a week after he was arrested and transported in a police van. (AP Photo/Patrick Semansky)  (The Associated Press)

  • Baltimore Mayor Stephanie Rawlings-Blake, center, speaks in front of local faith leaders at a news conference regarding the death of Freddie Gray, Friday, April 24, 2015, in Baltimore. Gray died from spinal injuries about a week after he was arrested and transported in a police van. (AP Photo/Patrick Semansky)

    Baltimore Mayor Stephanie Rawlings-Blake, center, speaks in front of local faith leaders at a news conference regarding the death of Freddie Gray, Friday, April 24, 2015, in Baltimore. Gray died from spinal injuries about a week after he was arrested and transported in a police van. (AP Photo/Patrick Semansky)  (The Associated Press)

  • Baltimore Mayor Stephanie Rawlings-Blake, back left, listens as Tessa Hill-Aston, president of the Baltimore chapter of the NAACP, speaks in front of local faith leaders at a news conference regarding the death of Freddie Gray, Friday, April 24, 2015, in Baltimore. Gray died from spinal injuries about a week after he was arrested and transported in a police van. (AP Photo/Patrick Semansky)

    Baltimore Mayor Stephanie Rawlings-Blake, back left, listens as Tessa Hill-Aston, president of the Baltimore chapter of the NAACP, speaks in front of local faith leaders at a news conference regarding the death of Freddie Gray, Friday, April 24, 2015, in Baltimore. Gray died from spinal injuries about a week after he was arrested and transported in a police van. (AP Photo/Patrick Semansky)  (The Associated Press)

Protesters are promising their biggest march yet a day after the Baltimore Police Department acknowledged that it failed to get Freddie Gray the medical attention he needed after his arrest.

Protesters vowed to "shut down" the city Saturday by marching through the streets and snarling traffic.

The president of a black lawyers' group predicted thousands of people would turn out for the demonstration, when good weather is forecast and the Baltimore Orioles host the Boston Red Sox.

Malik Shabazz of Black Lawyers for Justice has demanded the arrest of six officers involved in the arrest of Gray, who died Sunday a week after suffering a spinal injury while in police custody.

The officers are suspended with pay and under criminal investigation by their own department.