The vehicle used by the attackers of Dalit leader and Bhim Army chief Chandra Shekhar Aazad was recovered from a village in Uttar Pradesh's Saharanpur district, the police said on Thursday.
The police in Amethi district have also registered a case under Section 506 (criminal intimidation) of the Indian Penal Code (IPC) after it came to light that a Facebook page had issued a death threat to Aazad days before the attack.
Activists of the Bhim Army and Azad Samaj Party held a demonstration at Parivartan Chowk in Lucnow and demanded proper security for Aazad. They were later taken into custody by the police.
A bullet grazed the 36-year-old Bhim Army chief's abdomen when unidentified assailants opened fire at his car in Saharanpur's Deoband, where he had gone to attend a ritual at a supporter's home, on Wednesday evening.
The vehicle used by Aazad's attackers was seized from Miragpur village late on Wednesday night. The number plate of the car showed it was registered in Haryana, the police said.
Superintendent of Police (Dehat Saharanpur) Sagar Jain said Aazad is undergoing treatment at the Saharanpur district hospital and his condition is stated to be stable.
Heavy police deployment was seen on the hospital premises as Aazad's supporters started gathering there in large numbers, raising slogans and demanding the immediate arrest of the attackers.
Taking note of a death threat issued by a Facebook page called 'Kshatriya of Amethi' to Aazad days before the attack, the Amethi police registered a case at Gauriganj police station.
The police have taken cognisance of the Facebook post and registered a case against unidentified persons under Section 506 of the IPC and relevant provisions of the IT Act, said Mayank Dwivedi, deputy superintendent of police, Gauriganj.
A post was shared five days ago on the page stating that Aazad would be killed by the Thakurs of Amethi at a road crossing in broad daylight.
A post shared on the page on Thursday said Aazad was shot in the waist but "he will not survive next time". Aazad is a very clever man, he needs security, a bulletproof vehicle and jacket, it said.
It also warned that there will be a big movement if any innocent Rajput is framed for the attack.
Wrestlers Bajrang Punia and Sakshi Malik met Aazad at the hospital and enquired about his health.
Speaking to reporters later, Punia said those behind the attack on Aazad should be arrested as soon as possible.
In Lucknow, Bhim Army and Azad Samaj Party activists handed over to a government official a memorandum addressed to the governor demanding that Aazad's security be stepped up.
Azad Samaj Party's media in-charge Ajay Gautam told PTI that memorandums demanding Z-plus security for Aazad will be submitted to President Droupadi Murmu and Uttar Pradesh Chief Minister Yogi Adityanath.
Following the attack on Wednesday, Aazad was taken to a community health centre and later shifted to the district hospital.
In a video message on Wednesday night, Aazad, who hails from Ghadkhauli village in Saharanpur, appealed to his supporters to remain calm and said he would keep fighting constitutionally.