Freddie Gray should have received medical attention at the spot where he was arrested - before he was put inside a police van, authorities said Friday. Baltimore police have come under intense scrutiny after Gray was taken into custody and suffered an unexplained spinal injury that led to his death. Six officers have been suspended with pay as local police and federal authorities investigate. However, commissioner Anthony Batts has ruled out the possibility of his resignation. Scroll down for video . 'That's not going to happen': Baltimore police commissioner Anthony Batts ruled out his resignation despite that fact that his deputy admitted they should have sought medical attention for Freddie Gray . Batts addressed a news conference in Baltimore on Friday amid growing calls for him to step down . Concession: Police admit they should have sought medical help for Freddie Gray (pictured being detained on April 12) when he requested assistance in the police car. He was later pronounced dead . Commissioner Batts said the investigation is being refined and the picture is getting 'sharper and sharper.' He did not elaborate. As for calls for his resignation, he said: 'That's not going to happen.' Gray, who is black, was arrested April 12 after he made eye contact with officers and ran away, police said. Officers held him down, handcuffed him and loaded him into a police van. While inside, he became irate and leg cuffs were put on him, police have said. Gray died on Sunday, April 19, after he 'had his spine 80 per cent severed at his neck' while in police custody . Gray was not buckled in by a seat belt, a violation of the police department's policy. He asked for medical help several times, and after a 30-minute ride that included three stops, paramedics were called. At some point - either during his arrest or inside the van - he suffered a mysterious spinal injury. Authorities have not explained how or when it occurred. Deputy police commissioner Kevin Davis said Friday that Gray should have received medical attention at the spot of his arrest. Bystander video shows Gray screaming as officers carried him to the van, his legs appearing limp. After a week of protests, people angry over the death promised their biggest march Saturday, when they would try to 'shut down' the city. The demonstrators say Gray's death shows police mistreatment of blacks in Baltimore and throughout the country. The mayor thanked protesters for being peaceful so far. She expects the results of the investigation to be turned over to prosecutors in a week, and they will decide whether any criminal charges will be filed. 'I will not deny we have had a very long and complicated history on issues such as these,' Mayor Stephanie Rawlings-Blake said. 'But it's important to remember that we have an equally long history of peaceful and legal protest.' Asked if Gray's possible 'rough ride' is a one-off, the mayor said: 'It's clearly not a one-off. The reason we have the policy around seat belts in the police vans is because of an incident that happened previously,' referring to Dondi Johnson. He died of a fractured spine in 2005 after he was arrested for urinating in public and transported without a seat belt, with his hands cuffed behind his back. Baltimore Mayor Stephanie Rawlings-Blake speaks in front of local faith leaders at a news conference regarding the death of Freddie Gray on Friday. She appeared to support the police with her statements . Captain Erik Pecha of the Baltimore Police Department exchanges words with young demonstrators . More than 50 officers manned a barricade surrounding the station, separating them from the protesters . Protesters for Freddie Gray stand outside the Baltimore Police Department's Western District police station. The protest was peaceful, though some in the crowd hurled insults at the officers behind the fence, who stared back stone-faced . Angela Hazel (C) reacts near City Hall during a protest against the death of Freddie Gray Hazel said 'I lost my child to the streets, too. My only child...' The leader of a group of local ministers called on Batts to resign immediately. 'It seems that no one in the police department can explain what happened,' said the Rev. Alvin Gwynn Sr., president of the Interdenominational Ministerial Alliance of Baltimore. He said the police department is 'in disarray' and Batts has shown a 'lack of viable leadership capabilities.' The mayor appeared to back the police commissioner at her own news conference. 'Nickel rides' have caused spinal injuries in the past and Baltimore police epartment rules were updated nine days before Gray's arrest stating that all detainees shall be strapped in by seat belts or other device . The president of a black lawyers' group predicted thousands of people would turn out Saturday, when good weather is forecast and the Orioles are hosting the Boston Red Sox in a Major League Baseball game. 'Things will change on Saturday, and the struggle will be amplified,' said Malik Shabazz of Black Lawyers for Justice. Shabazz rejected the notion that he was an outside agitator who would stir up trouble. Bernard Young, Baltimore City Council president said prior to a rally on Thursday that he hoped citizens wouldn't let 'outside forces come in here and dictate how we act by destroying our infrastructure.' 'We can lead ourselves. We're capable of doing that,' he said.
Freddie Gray, who is black, asked for medical help but was denied during 30-minute police car ride, eventually paramedics were called .
Deputy police commissioner Kevin Davis conceded their failure .
But chief commissioner refuses to resign over the death .
Six officers are suspended without pay during an investigation .