Speaking to the media, Singh said the DCP cannot name a political party when the model code of conduct (MCC) is in place.
"I am shocked. The MCC is in place and the EC is the supreme authority. The DCP heading the investigation is saying that the photo of AAP leaders were found in the phone of the accused and they are probing the case. Is Amit Shah asking the DCP to make the statement or someone else is pushing him," Singh asked.
He said Deo is saying that the shooter, Kapil Gurjar, is part of AAP and has released a photo which allegedly shows the shooter with him. Singh said that AAP will send a legal notice to the DCP and file a complaint with the poll panel.
The AAP leader said that it was wrong for a police officer to name a political party when the investigation is not even completed.
"The law says that no official can name a (political) party until it has permission from the EC (when the MCC is imposed). Did the DCP take permission from the EC? No, he has the permission of (Home Minister Amit) Shah and the BJP," he said.
The Rajya Sabha MP also questioned as to how the photo was leaked to the media and the BJP while the probe was still going on.
"How the photo, if it was part of the investigation, reached the media and the BJP leaders? For the past three days, BJP was saying that AAP is involved (in the shooting). They have been saying that he belongs to AAP. Does that mean the BJP leaders were involved in the investigation," the AAP leader asked.
Singh also said that no matter what the BJP does, the people of Delhi will vote for AAP on February 8. "All this is happening because the BJP is scared of defeat," Singh said.
He also questioned if the presence of someone in a photo was a proof of that person being involved in the crime.
Singh released a photo of a man, allegedly an ISI agent, with BJP's Kailash Vijayvargiya and Prithviraj Chauhan and asked: "Does this mean the two BJP leaders have connection with the ISI and Pakistan?"
He showed another photo of self proclaimed godman Ram Rahim with Manohar Lal Kattar and Prakash Javedkar and asked the "did the cases for which the baba is in jail also apply to the two?"
Singh then showed a third photo of another self-proclaimed godman charged with rape alongside Rajyavardhan Singh Rathore and Chauhan, and again repeated his question.
He showed two more photos of Prime Minister Narendra Modi with Asaram Bapu and Chinmayanand also charged with rape and said that it cannot be a fact that Modi was involved in the crime.
He also said that the man who opened fire in Jamia on students had claimed on his Facebook profile that he is a member of the Bajrang Dal, asking "did the police even once say that he belongs to Bajrang Dal?"
"This is happening for the first time in the country that a DCP is saying that the police will see the role of a political party after a photo was found. I want to say that the probe should be done in an unbiased manner and the culprits should be put behind bars," he said.
The police should stop being a puppet on the hands of the BJP, Singh added.
He said that BJP leaders are so confused that on the one hand they are saying that AAP is serving biryani in Shaheen Bagh, while at the same time they are accusing the party of opening fire on the protesters. "They should first decide what they want to accuse us of," Singh said.
On the connection of Gurjar and his father with AAP, Singh said the party will first check if they have any designation. "We also have to see if they have switched their loyalties after joining the party."
"The elections are just four days away. Let's see how many more photos are released," Singh said.
( With inputs from IANS )